A fuel cell system having a fuel cell and gas supplying paths for supplying fluids such as a fuel gas or an oxide gas that are used by the fuel cell to cause electrochemical reaction is being developed.
For example, in a case of a fuel cell system using PEFC (Polymer Electrolyte Fuel Cell), difference in pressure between the air electrode and the fuel electrode may become large. Under such circumstances, undesirable conditions such as a degrading of electrolyte membrane of the fuel cell, or a decline in the durability of the fuel cell may happen. To prevent such undesirable conditions from happening, a technique to control the amount of hydrogen gas that is supplied to the fuel electrode side and the amount of oxide gas that is supplied to the air electrode side is being developed. By using such technique, the pressures of the air electrode side and the fuel electrode side of the fuel cell are maintained in a stable manner.
Japanese Patent Application Publication No. 2002-246045 discloses a fuel cell system that includes a primary regulator arranged at a gas exit of a hydrogen gas tank. A secondary regulator is arranged on a hydrogen gas supplying path that leads the hydrogen gas released through the primary regulator to the fuel cell. The secondary regulator is controlled in accordance with the operation status of the fuel cell. Furthermore, in the aforementioned fuel cell system, a bypass path is connected to the hydrogen gas supplying path. The bypass path communicates the upper stream side of the secondary regulator with the lower stream side of the secondary regulator. A shutoff valve is arranged on the bypass path. A controller controls the secondary regulator and the shutoff valve.
In the fuel cell system, the hydrogen gas inside the hydrogen gas tank is controlled to be at a predetermined pressure level by the primary regulator. The pressure of the hydrogen gas whose pressure has been controlled by the primary regulator is then further moderated by the secondary regulator. The secondary regulator is controlled in accordance with the operation status of the fuel cell. The secondary regulator adjusts the pressure amount of the hydrogen gas to be supplied to the fuel cell. With the aforementioned configuration, the pressure difference between the air electrode side and the fuel electrode side within the fuel cell is stably maintained. Undesirable conditions such as the degrading of electrolyte membrane of the fuel cell or the decline in the durability of the fuel cell are thus prevented.